CDMA/TDD mobile communication system and method

ABSTRACT

Control section  125  at base station  100  in a CDMA/TDD mobile communication system assigns one or more fixed forward link time slots to a plurality of time slots divided at a communication frame at a predetermined interval, and forward link time slots and reverse link time slots to the time slots except for the fixed forward link time slots by allocating corresponding to a ratio of a total information volume of a forward link to a total information volume of a reverse link in the system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slots, and to transmit forward link and reverse link traffic channel signals using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume.

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/264,826, filed on Mar. 9, 1999, which is hereby incorporatedby reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a CDMA/TDD mobile communicationsystem and method applying a same band transmission/reception system forassigning time slots at the same radio frequency band to communicateover a reverse link and a forward link alternately.

[0004] 2. Description of the Invention

[0005] Conventionally, as a mobile communication system using a CDMA(Code Division Multiple Access) system, a W-CDMA (Wideband CDMA) systemusing a DS (Direct Sequence) system is known. The W-CDMA system uses aFDD (Frequency Division Duplex) system as a duplex system.

[0006] As a duplex system, a TDD (Time Division Duplex) system is knownother than the FDD. The TDD system uses a same bandtransmission/reception system for assigning time slots at the same radiofrequency band to communicate a reverse link and a forward linkalternately, which is also called Ping-Pong system.

[0007] In addition, a multiple access system is a line connection systemover which a plurality of stations concurrently communicate at the samefrequency band. The CDMA system employs a technique for performing amultiple access by a spread spectrum communication in which informationsignals are spread by a spreading code to transmit over a spread band.In the DS system, information signals are multiplied by a spreading codein spreading.

[0008] In the DS-CDMA system, since a plurality of communication linksshare the same frequency band, there is a problem to control eachcommunication wave level at a reception to be equal (near-far problem).In other words, the conquest over this problem is necessary to achievethe CDMA communication system.

[0009] The near-far problem is severer at a reception of a base stationfor concurrently receiving radio signals transmitted from a plurality ofmobile stations (mobile radio terminal devices) each locating at adifferent place. Therefore, it is mandatory at the mobile stationpropagation path condition.

[0010] In the TDD system, propagation path conditions such as fadingcorrelate when intervals of forward and reverse links are short enoughbecause the same frequency band is used for the forward and reverselinks. It is thereby possible to perform a transmission power control byopen-loop control.

[0011] Some of such CDMA mobile communication system comprises a TDDconfiguration for dividing a communication frame into a plurality oftime slots to assign each of traffic channel and control channel to atime slot to communicate over a plurality of links.

[0012]FIG. 1 illustrates a frame diagram in a conventional CDMA/TDDmobile communication system.

[0013]FIG. 1 illustrates an example where one frame 1 is divided intoeight time slots 0 to 7, time slots 0 to 3 are assigned to a forwardlink and time slots 4 to 7 are assigned to a reverse link.

[0014] In forward link 2 toward a mobile station (not shown) from a basestation (not shown), common control channel 3 such as synchronizationcontrol channel, a dedicated control channel and user informationchannel 4 that are transmitted between the base station and a dedicatedmobile station are multiplexed. In reverse link 5 toward the basestation from the mobile station, the dedicated control channel and userinformation channel 6 are multiplexed.

[0015] The mobile station starts receiving when it is turned on, andacquires synchronization with the base station by detecting thesynchronization control channel of common control channel 3 in forwardlink 2. Then the mobile station performs a line connection via thededicated control channel to start communicating with user informationchannel 4. At this point, the mobile station measures reception qualityof an assigned forward link time slot, and based on the measurementresult, performs a transmission power control of an assigned reverselink time slot.

[0016] However, in the conventional CDMA/TDD mobile communication systemdescribed above, when an assignment of time slots to forward link andreverse link is changed corresponding to information volume of theforward and reverse links, a configuration of the synchronizationcontrol channel becomes irregular. It thereby takes a longer time for amobile station to acquire synchronization with a base station when it isturned on.

[0017] In addition, in each communication link, since an interval of theassigned forward link time slot and the assigned reverse link time slotis long, the propagation path conditions of the forward and reverselinks do not correlate so much, thereby decreasing an effect of anopen-loop controlled transmission power control.

SUMMARY OF THE INVENTION

[0018] It is an object of the present invention to provide a CDMA/TDDmobile communication system and method for enabling a synchronizationacquisition time with a base station at a mobile station to beshortened, and enabling open-loop controlled transmission power controlto function effectively when an assignment of time slots to forward andreverse links is changed corresponding to an information volume in thecase where the information volumes of the forward and reverse links areasymmetry.

[0019] The object is achieved by a CDMA/TDD mobile communication systemcomprising a base station apparatus having a control section forassigning one or more fixed forward link time slots to a plurality oftime slots divided at a communication frame at a predetermined interval,while assigning forward link time slots and reverse link time slots tothe time slots except for the fixed forward link time slots byallocating the time slots corresponding to a ratio of a totalinformation volume of a forward link to a total information volume of areverse link in the system, in order to transmit a control channelsignal including a synchronization control channel signal using thefixed forward link time slots, and to transmit a traffic channel signalof the forward link and a traffic channel signal of the reverse linkrespectively using the forward link time slots and the reverse link timeslots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a frame diagram applied in a conventional CDMA/TDDmobile communication system;

[0021]FIG. 2 is block diagram of a base station in a CDMA/TDD mobilecommunication system according to a first embodiment of the presentinvention;

[0022]FIG. 3 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in the CDMA/TDD mobile communicationsystem according to the first embodiment of the present invention;

[0023]FIG. 4 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to a second embodiment of the present invention;

[0024]FIG. 5 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to a third embodiment of the present invention;

[0025]FIG. 6 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to a fourth embodiment of the present invention;

[0026]FIG. 7 is a block diagram of a mobile station in a CDMA/TDD mobilecommunication system according to a fifth embodiment of the presentinvention;

[0027]FIG. 8 is an integration result diagram obtained by the mobilestation according to the fifth embodiment integrating correlation valueof a received signal with a spreading code of a forward synchronizationcontrol channel at each sampling timing over four time slots intervalstarting from an arbitrary time.

[0028]FIG. 9 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to a sixth embodiment of the present invention; and

[0029]FIG. 10 is a frame diagram illustrating an assignment of timeslots at a communication frame applied in a CDMA/TDD mobilecommunication system according to a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] A CDMA/TDD mobile communication system and method according tothe embodiments of the present invention are specifically explainedbelow with reference to attached drawings.

[0031] (First Embodiment)

[0032]FIG. 2 is block diagram of a base station in a CDMA/TDD mobilecommunication system according to the first embodiment of the presentinvention.

[0033] Base station 100 illustrated in FIG. 2 is composed of codingsection 104 having first coding section 101, second coding section 102and third coding section 103, spreading section 108 having firstspreading section 105, second spreading section 106 and third spreadingsection 107, multiplexing section 109, D/A conversion section 110,transmission frequency conversion section 111, reception frequencyconversion section 112, A/D conversion section 113, allocating section114, correlation detection section 118 having first correlationdetection section 115, second correlation detection section 116, andthird correlation detection section 117, decoding section 122 havingfirst decoding section 119, second decoding section 120 and thirddecoding section 121, transmission/reception antenna 123,transmission/reception switching section 124 and control section 125.

[0034] Coding sections 101 to 103 execute coding of first to thirdforward link dedicated control channel signals 131, 132 and 133respectively. Spreading sections 105 to 107 executed spreading the codedchannel signals 134, 135 and 136 respectively.

[0035] Multiplexing section 109 multiplexes the spread channel signals137 to 139. D/A conversion section 110 converts the multiplexed signal140 into analogue signal 141. Transmission frequency conversion section111 converts the analogue signal 141 into transmission signal 142 withradio frequency.

[0036] Transmission/reception switching section 124 switchestransmission/reception antenna 123 for a transmission site and atransmission site to connect. The transmission signal 142 is transmittedfrom transmission/reception antenna through transmission/receptionswitching section 124 to a mobile station (not shown).

[0037] The reception frequency conversion section 112 converts receivedsignal 431 with radio frequency into signal 144 with baseband frequency.The received signal 431 is received at transmission/reception antenna123 and transmitted through transmission/reception switching section 124to the section 112.

[0038] A/D conversion section 113 converts the signal 144 with basebandfrequency into digital received signal 145. Allocating section 114allocates digital received signal 145 to channel signals 146, 147 and148.

[0039] Correlation detection sections 115 to 117 detect correlation ofreverse link common dedicated channel signals 146 to 148 respectively.Decoding sections 119 to 121 decode correlation detection channelsignals 149, 150 and 151 to output channel decoded signals 152, 153 and154. Control section 125 controls over each section described above.

[0040] In a configuration described above, forward link common channel(such as synchronization control channel) signals 131 to 133 are codedand constructed into frames at coding sections 101 to 103 and output tospreading sections 105 to 107 respectively. The coding may be an errorcorrection coding, and in this case, interleaving processing is alsoexecuted.

[0041] Spreading sections 105 to 107 respectively spread coded channelsignals 134 to 136 with a spreading code to output spread signals 137 to139 to multiplexing section 109. The spreading code may be assigned fromcontrol section 125.

[0042] Multiplexing section 109 provides spread signals 137 to 139 attime slots to multiplex according to an instruction from control section125. At this stage, channel signals provided at the same time slot aremultiplexed. In the case where the multiplexing processing is executed,a transmission power control may be performed to control an amplitude ofeach of channel spread signals 137 to 139.

[0043] Digital multiplexed signal 140 is converted into analogue signal141 in D/A conversion section 110. The analogue signal 141 is convertedinto transmission signal 142 with radio frequency in transmissionfrequency conversion section 111. The transmission signal 142 istransmitted from transmission/reception antenna 123 throughtransmission/reception switching section 124.

[0044] At this stage, transmission/reception switching section 124connects transmission/reception antenna 123 to transmission frequencyconversion section 111 for a forward link time slot and to receptionfrequency conversion section 112 for a reverse link time slot accordingto an Instruction from control section 125.

[0045] On the other hand, reception signal 143, which is received attransmission/reception antenna 123 from a mobile station, is input toreception frequency conversion section 112 throughtransmission/reception switching section 124. Reception frequencyconversion section 112 converts the received signal 143 with radiofrequency into signal 144 with baseband frequency.

[0046] A/D conversion section 113 converts the analogue signal 144 withbaseband frequency into digital signal 145 to output to allocatingsection 114. Allocating section 114 divides the digital signal 145 intoreverse common control channel signals 146 to 148 according to aninstruction of control section 125 to output to correlation detectionsections 115 to 117 respectively.

[0047] Correlation detection sections 115 to 117 despread the reversecommon control channel signals 146 to 148 to detect correlation of areceived signal with a spreading code. Each spreading code may beinstructed by control section 125.

[0048] Detected correlation values (correlation signals) 149 to 151 arerespectively output to decoding sections 119 to 121, which decodereverse common control channel signals based on correlation values 149to 151. At this stage, when a mobile station executes an errorcorrection coding for a reverse link, an error correction decoding withdeinterleaving processing is executed.

[0049] In addition, each common section may be provided to use for allchannels according to time slots instead of using coding sections 101 to103, spreading sections 105 to 107, correlation detection sections 115to 117, and decoding sections 119 to 121.

[0050] An assignment control of time slots is explained from amongcontrols executed by control section 125 with reference to FIG. 3. FIG.3 is a frame diagram illustrating an assignment of time slots at acommunication frame in a CDMA/TDD mobile communication system. Theassignment illustrates an example where one frame 201 is divided into 16time slots 0 to 15.

[0051] In FIG. 3, 202 indicates a time slot at which a forward linkcommon control channel signal and a forward link user informationchannel signal are provided, 203 indicates a time slot at which only aforward link user information channel signal is provided, and 204indicates a time slot at which a reverse link channel signal isprovided.

[0052] Control section 125 first compares an information volume of theforward link with that of reverse link and determines the numbers oftime slots to be assigned to the forward link and the reverse link. Atthis point, the number of time slots necessary to transmit a forwardlink common control channel signal including a synchronization controlchannel signal is primarily assigned to the forward link. The other timeslots are assigned to the forward link and reverse link taking theinformation volumes into consideration.

[0053] Then, the forward link common control channel signal includingthe synchronization control channel signal is provided at a time slot ata predetermined time slots interval at a frame, accordingly the timeslot is assigned for a forward link time slot.

[0054] Further, the rest of forward link time slots are provided at theframe. At this point, the forward link time slots are provided primarilyat time slots except for those following just after the forward linktime slots to transmit control channel signals including synchronizationcontrol channel signals. Then the other time slots are assigned for thereverse link time slots.

[0055] In the forward link time slots at which forward link commoncontrol channel signals including synchronization control channelsignals are provided, the forward link common control channel signalsmay be not only provided, but also other forward link channel signalsmay be provided. In this case, a plurality of channel signals providedin the time slot are multiplexed to transmit.

[0056]FIG. 3 illustrates examples of assigning sixteen time slots at aframe.

[0057] (A) in FIG. 3 illustrates the case where four time slots 0, 4, 8and 12 are assigned for forward link time slots, and the other twelvetime slots are assigned for reverse link time slots.

[0058] (B) in FIG. 3 illustrates the case where eight time slots areassigned for forward link time slots, and the other eight time slots areassigned for reverse link time slots. The times slots 0, 4, 8 and 12 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 2, 6, 10 and 14 are further assigned forforward link time slots. The time slots 1, 3, 5, 7, 9, 11, 13 and 15 areassigned for reverse link time slots.

[0059] (C) in FIG. 3 illustrates the case where twelve time slots areassigned for forward link time slots, and the other four time slots areassigned for reverse link time slots. The time slots 0, 4, 8 and 12 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 2, 3, 6, 7, 10, 11, 14 and 15 are furtherassigned for forward link time slots. The time slots 1, 5, 9, and 13 areassigned for reverse link time slots.

[0060] (D) in FIG. 3 illustrates the case where fifteen time slots areassigned for forward link time slots, and the other one time slot isassigned for a reverse link time slot. The time slots 0, 4, 8 and 12 areassigned for the forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 2, 3, 5, 6, 7, 9, 10, 11, 13, 14 and 15 arefurther assigned for forward link time slots. The time slot 1 isassigned for the reverse link time slot.

[0061] In (c) and (D) in FIG. 3, the reverse link time slots arepositioned just after the time slots assigned for forward link timeslots to transmit common control channel signals includingsynchronization control channel signals. As a result, in the case wherea closed-loop control is performed in the system, it is possible for amobile station to control transmission power using a TPC bit containedin the control channel signal in the received forward link commoncontrol channel signal. Accordingly, the mobile station can respondrapidly to a propagation environment such as fading.

[0062] The assignment of time slots may be changed manuallycorresponding to a change of an information volume, or changedautomatically according to the change of the information volume causedby a new connection or a break, or at predetermined intervals.

[0063] A mobile station acquires synchronization with a base stationwhen it is turned on by first despreading a received signal with aspreading code used in the synchronization control channel signal todetect the synchronization control channel signal.

[0064] Under such condition, the mobile station does not know anassignment of lime slots for a forward link and a reverse link when itis turned on, however knows in advance that a synchronization controlchannel signal is positioned once every four slots with three time slotsinserted. Therefore, the mobile station can detect a timing of thesynchronization control channel signal by integrating correlation valuesover every four time slots interval.

[0065] The mobile station decodes the common control channel signalincluding the synchronization control channel signal using the detectedtiming in order to recognize positions of forward link time slots andreverse link time slots and time slots assigned to each channel.

[0066] Then the mobile station performs connection processing using therecognized common control channel and dedicated control channel toestablish a user information channel. Signals of user informationchannel between a mobile station and a base station are provideddifferently for a forward link and a reverse link at a frame 201.Therefore, the time difference between a forward link user informationchannel time slot and a reverse link user information channel time slotis sometimes large with the other many time slots inserted between thosetime slots.

[0067] In the case of performing a reverse link transmission powercontrol using an open-loop control, since the correlation characteristicof propagation path conditions of a forward link and a reverse link isused, the large time difference introduces the low correlationcharacteristic, resulting in a reduced accuracy of the transmissionpower control.

[0068] However, since the forward link common control channel signal istransmitted every four time slots, when a reception quality is measuredusing the forward link common control channel signal and thetransmission power control is performed based on the measured receptionquality, the time difference between the forward link time slot used tomeasure the reception quality and the reverse link time slot to betransmitted under the transmission power control are a two time slotstime at maximum, thereby enabling an efficient transmission powercontrol.

[0069] In addition, It is preferable to use the arbitrary number of timeslots composing a frame other than sixteen. It is also preferable toprovide a forward link common control channel signal every arbitrarynumber of time slots other than every four time slots. It is furtherpreferable to provide a forward link common control channel signal at apredetermined periodical pattern other than at equal intervals.

[0070] As described above, according to the first embodiment, under thecontrol of control section 125 in base station 100, some of time slotsat a communication frame are assigned primarily to fixed forward linktime slots at predetermined intervals and the other time slots areallocated to forward link time slots and reverse link time slotscorresponding to a ratio of the total information volume of the reverselink to that of the forward link in a system, in order to transmit acontrol channel signal including a synchronization control channelsignal using the fixed forward link time slot and transmit trafficchannel signals of forward link and reverse link respectively using theforward link time slots and the reverse link time slots that areallocated according to the number of time slots respectively requiredcorresponding to the respective information volume. The above processingmakes it possible to shorten a time for a mobile station to acquiresynchronization with a base station even when an assignment of timeslots for forward and reverse links is changed corresponding to theinformation volumes of forward link and reverse link in the case wherethe information volumes are asymmetry, thereby enabling an open-loopcontrolled transmission power control to function effectively.

[0071] (Second Embodiment)

[0072]FIG. 4 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to the second embodiment of the present invention.

[0073]FIG. 4 illustrates an example where one frame 301 is divided intosixteen time slots 0 to 15. In FIG. 4, the reference number 302indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 303 indicate a time slot at which only a forwardlink user information channel signal is provided, and the referencenumber 304 indicate a time slot at which a reverse link channel signalis provided.

[0074] Control section 125 of base station 100 illustrated in FIG. 2first compares an information volume of the forward link with that ofreverse link and determines the numbers of time slots to be assigned tothe forward link and the reverse link.

[0075] At this point, the number of time slots necessary to transmit aforward link common control channel signal including a synchronizationcontrol channel signal is primarily assigned to the forward link. Theother time slots are assigned to the forward link and reverse linktaking the information volumes into consideration.

[0076] Then, the forward link common control channel signal includingthe synchronization control channel signal is provided at a slot everytwo slots with a slot inserted, accordingly the time slot is assignedfor a forward link time slot. Further, the other forward link time slotsare provided at the frame, and the rest of the time slots are assignedfor reverse link time slots.

[0077] In the forward link time slots at which forward link commoncontrol channel signals including synchronization control channelsignals are provided, the forward link common control channel signalsincluding synchronization control channel signals may be not onlyprovided, but also other forward link channel signals may be provided.In this case, a plurality of channel signals provided in the same timeslot are multiplexed to transmit.

[0078] (A) in FIG. 4 illustrates the case where eight time slots areassigned for forward link time slots, and the other eight time slots areassigned for reverse link time slots. The time slots 0, 2, 4, 6, 8, 10,12 and 14 are assigned for forward link time slots to transmit forwardlink common control channel signals including synchronization controlchannel signals, and the time slots 1, 3, 5, 7, 9, 11, 13 and 15 areassigned for reverse link time slots.

[0079] (B) in FIG. 4 illustrates the case where twelve time slots areassigned for forward link time slots, and the other eight time slots areassigned for reverse link time slots. The time slots 0, 2, 4, 6, 8, 10,12 and 14 are assigned for forward link time slots to transmit forwardlink common control channel signals including synchronization controlchannel signals and the time slots 1, 5, 9 and 13 are further assignedfor forward link time slots. The time slots 3, 7, 11, and 15 areassigned for reverse link time slots.

[0080] (C) in FIG. 4 illustrates the case where fourteen time slots areassigned for forward link time slots, and the other two time slots areassigned for reverse link time slots. The time slots 0, 2, 4, 6, 8, 10,12 and 14 are assigned for forward link time slots to transmit forwardlink common control channel signals including synchronization controlchannel signals and the time slots 1, 3, 5, 9, 11 and 13 are furtherassigned for forward link time slots. The time slots 7 and 15 areassigned for reverse link time slots.

[0081] (D) in FIG. 3 illustrates the case where fifteen time slots areassigned for forward link time slots, and the other one slot is assignedfor a reverse link time slot. The time slots 0, 2, 4, 6, 8, 10, 12 and14 are assigned for forward link time slots to transmit forward linkcommon control channel signals including synchronization control channelsignals and the time slots 1, 3, 5, 7, 9, 11 and 13 are further assignedfor forward link time slots. The time slot 15 is assigned for a reverselink time slot.

[0082] As describe above, in FIG. 4, time slots provided just after timeslots to transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

[0083] In other words, by providing one of time slots to transmitforward link common control channel signals including synchronizationcontrol channel signals every two time slots, i.e., with one other timeslot inserted between those, ever when reverse time slots are providedin any time slots, it is configured that the time slots just before thereverse link time slots are always the forward link time slots totransmit common control channel signals including synchronizationcontrol channel signals.

[0084] Therefore, in the case where a closed-loop control is performedin the system, it is possible for a mobile station to controltransmission power using a TPC bit contained in the control channelsignal in the received forward link common control channel signal.Accordingly, the mobile station can respond rapidly to a propagationenvironment such as fading.

[0085] The assignment of time slots may be changed manuallycorresponding to a change of an information volume, or changedautomatically according to the change of the information volume causedby a new connection or a break, or at predetermined intervals.

[0086] Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to detect the synchronizationcontrol channel signal.

[0087] The mobile station does not know an assignment of time slots fora forward link and a reverse link when it is turned on, however themobile station can detect a timing of the synchronization controlchannel signal by integrating correlation values over every two timeslots interval.

[0088] Then, the mobile station decodes the common control channelsignal including the synchronization control channel signal using thedetected timing in order to recognize positions of forward link timeslots and reverse, link time slots and time slots assigned to eachchannel, and performs connection processing using the recognized commoncontrol channel and dedicated control channel to establish a userinformation channel.

[0089] User information channel slots between a mobile station and abase station are positioned differently for forward link and reverselink at a frame. Therefore, the time difference between a forward linkuser information channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

[0090] In the case of performing a reverse link transmission powercontrol using an open-loop control, the large time difference introducesthe low correlation characteristic of propagation path conditions of theforward link and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every two slots, when the transmission power control isperformed based on the reception quality obtained by using the receivedcommon control channel, it is possible to use the reception quality ofthe forward link time slot just before the reverse link time slot to betransmitted under the transmission power control, thereby enabling aneffective transmission power control. In addition, it is also preferableto use the arbitrary number of time slots composing a frame other thansixteen.

[0091] As described above, according to the second embodiment, a timeslot in every two slots is assigned for a fixed forward link time slotand the other time slots are allocated for forward link time slots andreverse link time slots corresponding to a ratio of the totalinformation volume of forward link to that of the reverse link in asystem, in order to transmit a control channel signal including asynchronization control channel signal using the fixed forward link timeslot and transmit traffic channel signals of forward link and reverselink respectively using the forward link time slots and the reverse linktime slots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume. The above processing makes it possible to shorten a time for amobile station to acquire synchronization with a base station even whenan assignment of time slots for forward and reverse links is changedcorresponding to the information volumes of forward link and reverselink when the information volumes are asymmetry, thereby enabling anopen-loop controlled transmission power control to function effectively.

[0092] (Third Embodiment)

[0093]FIG. 5 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to the third embodiment of the present invention.

[0094]FIG. 5 illustrates an example where one frame 401 is divided intosixteen time slots 0 to 15. In FIG. 5, the reference number 402indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 403 indicates a time slot at which a forward linkuser information channel signal is provided, and the reference number404 indicates a time slot at which a reverse link channel signal isprovided.

[0095] Control section 125 of base station 100 illustrated in FIG. 2first compares an information volume of the forward link with that ofreverse link and determines the numbers of time slots to be assigned tothe forward link and the reverse link.

[0096] At this point, the number of time slots necessary to transmit aforward link common control channel signal including a synchronizationcontrol channel signal is primarily assigned to the forward link. Theother time slots are assigned to the forward link and reverse linktaking the information volumes into consideration.

[0097] Then, the forward link common control channel signal including hesynchronization control channel signal is provided at a slot every eighttime slots with seven time slots inserted, accordingly the time slot isassigned for a forward link time slot. Further, the other forward linktime slots are provided at the frame, and the rest of time slots areassigned for reverse link time slots.

[0098] In the forward link time slots at which forward link commoncontrol channel signals including synchronization control channelsignals are provided, the forward link common control channel signalsincluding synchronization control channel signals may be not onlyprovided, but also other forward link channel signals may be provided.In this case, a plurality of channel signals provided in the same timeslot are multiplexed to transmit.

[0099] (A) in FIG. 5 illustrates the case where two time slots areassigned for forward link time slots, and the other fourteen time slotsare assigned for reverse link time slots. The time slots 0 and 8 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals. The other time slots 1 to 7 and 9 to 15 are assigned forreverse link time slots.

[0100] (B) in FIG. 5 Illustrates the case where eight time slots areassigned for forward link time slots, and the other eight time slots areassigned for reverse link time slots. The time slots 0 and 8 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 2, 4, 6, 10, 12 and 14 are further assignedfor forward link time slots. The time slots 1, 3, 5, 7, 9, 11, 13 and 15are assigned for reverse link time slots.

[0101] (C) in FIG. 5 illustrates the case where twelve time slots areassigned for forward link time slots, and the other four time slots areassigned for reverse link time slots. The time slots 0 and 8 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 2, 3, 4, 6, 7, 10, 11, 12, 14 and 15 arefurther assigned for forward link time slots. The time slots 1, 5, 9 and13 are assigned for reverse link time slots.

[0102] (D) in FIG. 5 illustrates the case where fifteen time slots areassigned for forward link time slots, and the other one time slot isassigned for a reverse link time slot. The time slots 0 and 8 areassigned for forward link time slots to transmit forward common controlchannel signals including synchronization control channel signals andthe time slots 2 to 7 and 9 to 15 are further assigned for forward linktime slots. The other time slot 15 is assigned for a reverse link timeslot.

[0103] As describe above, in FIG. 5, time slots provided just after timeslots to transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

[0104] In other words, by providing one of time slots to transmitforward link common control channel signals including synchronizationcontrol channel signals every eight time slots, i.e., with seven othertime slots inserted between those, even though reverse time slots areprovided at any time slots, it is configured that the time slot justbefore at least one of the reverse link time slots at a frame is alwaysa forward link time slot to transmit common control channel signalsincluding synchronization control channel signals.

[0105] Therefore, in the case where a closed-loop control is performedin the system, it is possible for a mobile station to controltransmission power using a TPC bit contained in the control channelsignal in the received forward link common control channel signal.Accordingly, the mobile station can respond rapidly to a propagationenvironment such as fading.

[0106] The assignment of time slots may be changed manuallycorresponding to a change of an information volume, or changedautomatically according to the change of the information volume causedby a new connection or a break, or at predetermined intervals.

[0107] Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to detect the synchronizationcontrol channel signal.

[0108] The mobile station does not know an assignment of time slots fora forward link and a reverse link when it is turned on, however themobile station can detect a timing of the synchronization controlchannel signal by integrating correlation values over every eight timeslots intervals.

[0109] Then, the mobile station decodes the common control channelsignal including the synchronization control channel signal using thedetected timing in order to recognize positions of forward link timeslots and reverse link time slots and time slots assigned to eachchannel, and performs connection processing using the recognized commoncontrol channel and dedicated control channel to establish a userinformation channel.

[0110] User information channel slots between a mobile station and abase station are positioned differently for forward link and reverselink at a frame. Therefore, the time difference between a forward linkuser information channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

[0111] In the case of performing a reverse link transmission powercontrol using an open-loop control, the large time difference introducesthe low correlation characteristic of propagation path conditions of theforward link and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every eight slots, when the transmission power controlis performed based on the reception quality obtained by using thereceived common control channel, it is possible to use the receptionquality of the forward Iink time slot just before the reverse link timeslot to be transmitted under the transmission power control, therebyenabling an effective transmission power control. In addition, it isalso preferable to use the arbitrary number of time slots composing aframe other than sixteen.

[0112] As described above, according to the third embodiment, a timeslot in every eight slots is assigned for a fixed forward link time slotand the other time slots are allocated for forward link time slots andreverse link time slots corresponding to a ratio of the totalinformation volume of reverse link to that of the forward link in asystem, in order to transmit a control channel signal including asynchronization control channel signal using the fixed forward link timeslot and transmit traffic channel signals of forward link and reverselink respectively using the forward link time slots and the reverse linktime slots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume. The above processing makes it possible to shorten a time for amobile station to acquire synchronization with a base station even whenan assignment of time slots for forward and reverse links is changedcorresponding to the information volumes of forward link and reverselink in the case where the information volumes are asymmetry, therebyenabling an open-loop controlled transmission power control to functioneffectively. In this case, it is possible to obtain many variations ofallocation configuration of the number of forward link time slots andthe number of reverse link time slots.

[0113] (Fourth Embodiment)

[0114]FIG. 6 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to the fourth embodiment of the present invention.

[0115]FIG. 6 illustrates an example where one frame 501 is divided intosixteen time slots 0 to 15. In FIG. 6, the reference number 502indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 503 indicates a time slot at which a forward linkuser information channel signal is provided, and the reference number504 indicates a time slot at which a reverse link channel signal isprovided.

[0116] Control section 125 of base station 100 illustrated in FIG. 2first compares an information volume of the forward link with that ofreverse link and determines the numbers of time slots to be assigned tothe forward link and the reverse link.

[0117] At this point, the number of time slots necessary to transmit aforward link common control channel signal including a synchronizationcontrol channel signal is primarily assigned to the forward link. Theother time slots are assigned to the forward link and reverse linktaking the information volumes into consideration.

[0118] Then, the forward link common control channel signal includingthe synchronization control channel signal is provided at a slot inevery sixteen slots, accordingly the time slot is assigned for a forwardlink time slot. Further, the other forward link time slots are providedat the frame, and the rest of time slots are assigned for reverse linktime slots.

[0119] In the forward link time slots at which forward link commoncontrol channel signals including synchronization control channelsignals are provided, the forward link common control channel signalsincluding synchronization control channel signals may be not onlyprovided, but also other forward link channel signals may be provided.In this case, a plurality of channel signals provided in the time slotare multiplexed to transmit.

[0120] (A) in FIG. 6 illustrates the case where one time slot isassigned for a forward link time slot, and the other fifteen time slotsare assigned for reverse link time slots. The time slot 0 is assignedfor a forward link time slot to transmit forward link common controlchannel signals including synchronization control channel signals. Theother time slots 1 to 15 are assigned for reverse link time slots.

[0121] (B) in FIG. 4 illustrates the case where eight time slots areassigned for forward link time slots, and the other eight time slots areassigned for reverse link time slots. The time slot 0 is assigned for aforward link time slot to transmit forward link common control channelsignals including synchronization control channel signals and the timeslots 2, 4, 6, 8, 10, 12 and 14 are further assigned for forward linktime slots. The time slots 1, 3, 5, 7, 9, 11, 13 and 15 are assigned forreverse link time slots.

[0122] (C) in FIG. 6 illustrates the case where twelve time slots areassigned for forward link time slots, and the other four time slots areassigned for reverse link time slots. The time slot 0 is assigned for aforward link time slot Lo transmit common control channel signalsincluding synchronization control channel signals and the time slots 2,3, 4, 6, 7, 8, 10, 11, 12, 14 and 15 are further assigned for forwardlink time slots. The time slots 1, 5, 9 and 13 are assigned for reverselink time slots.

[0123] (D) in FIG. 3 illustrates the case where fifteen time slots areassigned for forward link time slots, and the other one time slot isassigned for reverse link time slots. The time slot 0 is assigned for aforward link time slot to transmit common control channel signalsincluding synchronization control channel signals and the time slots 2to 15 are further assigned for forward link time slots. The time slot 1is assigned for a reverse link time slot.

[0124] As describe above, in FIG. 6, time slots provided just after timeslots to transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

[0125] In other words, by providing one of time slots to transmitforward link common control channel signals including synchronizationcontrol channel signals every sixteen time slots, i.e., with fifteenother time slots inserted between those, even though reverse time slotsare provided in any time slots, it is configured that the time slot justbefore at least one of the reverse link time slots at a frame is alwaysa forward link time slot to transmit common control channel signalsincluding synchronization control channel signals.

[0126] Therefore, in the case where a closed-loop control is performedin the system, it is possible for a mobile station to controltransmission power using a TPC bit contained in the control channelsignal in the received forward link common control channel signal.Accordingly, the mobile station can respond rapidly to a propagationenvironment such as fading.

[0127] The assignment of time slots may be changed manuallycorresponding to a change of an information volume, or changedautomatically according to the change of the information volume causedby a new connection or a break, or at predetermined intervals.

[0128] Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to detect the synchronizationcontrol channel signal.

[0129] The mobile station does not know an assignment of time slots fora forward link and a reverse link when it is turned on, however themobile station can detect a timing of the synchronization controlchannel signal by integrating correlation values over every fifteen timeslots intervals.

[0130] Then, the mobile station decodes the common control channelsignal including the synchronization control channel signal using thedetected timing in order to recognize positions of forward link timeslots and reverse link time slots and time slots assigned to eachchannel, and performs connection processing using the recognized commoncontrol channel and dedicated control channel to establish a userinformation channel.

[0131] User information channel slots between a mobile station and abase station are positioned differently for forward link and reverselink at a frame. Therefore, the time difference between a forward linkuser information channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

[0132] In the case of performing a reverse link transmission powercontrol using an open-loop control, the large time difference introducesthe low correlation characteristic of propagation path conditions of theforward link and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every sixteen slots, when the transmission powercontrol is performed based on the reception quality obtained by usingthe received common control channel, it is possible to use the receptionquality of the forward link time slot just before the reverse link timeslot to be transmitted under the transmission power control, therebyenabling an effective transmission power control. In addition, it isalso preferable to use the arbitrary number of time slots composing aframe other than sixteen.

[0133] As described above, according to the fifth embodiment, a timeslot in every sixteen slots is assigned for a fixed forward link timeslot and the other time slots are allocated for forward link time slotsand reverse link time slots corresponding to a ratio of the totalinformation volume of reverse link to that of the forward link in asystem, in order to transmit a control channel signal including asynchronization control channel signal using the fixed forward link timeslot and transmit traffic channel signals of forward link and reverselink respectively using the forward link time slots and the reverse linktime slots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume. The above processing makes it possible to shorten a time for amobile station to acquire synchronization with a base station even whenan assignment of time slots for forward and reverse links is changedcorresponding to the information volumes of forward link and reverselink in the case where the information volumes are asymmetry, therebyenabling an open-loop controlled transmission power control to functioneffectively. In this case, it is possible to obtain many variations ofallocation configuration of the number of forward link time slots andthe number of reverse link time slots.

[0134] (Fifth Embodiment)

[0135]FIG. 7 is block diagram of a mobile station as an example ofcommunication terminal devices in a CDMA/TDD mobile communication systemaccording to the fifth embodiment of the present invention.

[0136] Mobile station 600 illustrated in FIG. 7 is composed of codingsection 601, spreading section 602, amplifying section 603, D/Aconversion section 640, transmission frequency conversion section 605,reception frequency conversion section 606, A/D conversion section 607,allocating section 608, correlation detection section 611 includingfirst correlation detection section 609, and second correlationdetection section 610, decoding section 614 including first decodingsection 612 and second decoding section 613, transmission/receptionantenna 615, transmission/reception switching section 616 and controlsection 617.

[0137] Coding section 601 codes reverse link channel signal 621.Spreading section 602 spreads coded signal 622. Amplifying section 603amplifies spread signal 623.

[0138] D/A conversion section 604 converts digital amplified signal 624into analogue signal 625. Transmission frequency conversion section 605converts the analogue signal 625 into transmission signal 626 with radiofrequency.

[0139] Transmission/reception switching section 616 switchestransmission/reception antenna 615 for a transmission site and atransmission site to connect. The transmission signal 626 is transmittedfrom transmission/reception antenna 615 through transmission/receptionswitching section 616 to a base station illustrated in FIG. 2 by radiocommunication.

[0140] Reception frequency conversion section 606 converts receivedsignal 627 with radio frequency into signal 628 with baseband frequency.The received signal 627 is received at transmission/reception antenna615 and transmitted through transmission/reception switching section 616to the section 606.

[0141] A/D conversion section 607 converts the signal 628 with basebandfrequency into digital received signal 629. Allocating section 608allocates the digital received signal 629 to channel signals 630 and631.

[0142] Correlation detection sections 609 and 610 detect respectivelyforward link common dedicated channel signals 630 and 631. Decodingsections 612 and 613 decode channel correlation detection signals 632and 633 to output channel decoded signals 634 and 635 respectively.Control section 617 controls over each section described above.

[0143] In a configuration described above, reverse link channel signal612 is coded and constructed into frames at coding section 602 andoutput to spreading section 602. The coding may be an error correctioncoding, and in this case, interleaving processing is also executed.

[0144] Spreading section 602 spreads coded signal 622 with a spreadingcode and outputs spread signal 623 to amplifying section 603. Thespreading code may be assigned from control section 617.

[0145] Amplifying section 603 provides the spread signal 623 at a timeslot assigned according to an instruction from control section 617 andperforms transmission power control by amplifying or decreasing anamplitude of the spread signal 623 according to an instruction fromcontrol section 617 to output to D/A conversion section 604.

[0146] D/A conversion section 604 converts digital amplified 624 intoanalogue signal 625 to output to transmission frequency conversionsection 605. Transmission frequency conversion section 605 converts theanalogue signal 625 into transmission signal 626 with radio frequency tooutput to transmission/reception switching section 616.

[0147] Transmission/reception switching section 616 connectstransmission/reception antenna 615 to transmission frequency conversionsection 605 for a reverse link time slot and to reception frequencyconversion section 606 for a forward link time slot according to aninstruction from control section 617.

[0148] In other words, with respect to reverse link time slots,transmission signal 626, which is subjected to the conversion offrequency into the radio frequency at reception frequency conversionsection 605, is transmitted from transmission/reception antenna 123 to abase station 100.

[0149] On the other hand, with respect to forward link time slots,received signal 627 that is received at transmission/reception antenna123 is input to reception frequency conversion section 606.

[0150] Reception frequency conversion section 606 converts the receivedsignal 627 with radio frequency into received signal 628 with basebandfrequency to output to A/D conversion section 607. A/D conversionsection 607 converts the analogue signal 628 into digital signal 629 tooutput to allocating section 608.

[0151] Allocating section 608 divides digital signal 629 into signals630 and 631 according to an instruction from control section 617 tooutput to correlation detection sections 609 and 610 respectively.

[0152] Correlation detection sections 609 and 610 despread dividedsignals 630 and 631 respectively to detect correlation of a receivedsignal with a spreading code and obtain correlation values 632 and 633respectively. Each spreading code may be instructed from control section125. Detected correlation values 632 and 633 are respectively output todecoding sections 612 and 613, while output to control section 617.

[0153] Decoding sections 612 and 613 decode forward common controlchannel signals 634 and 635 using correlation values 632 and 633. Atthis point, when base station 100 executes an error correction codingfor a forward link, an error correction decoding with deinterleavingprocessing is executed.

[0154] In addition, each common section may be provided to use for allchannels according to time slots instead of using correlation detectionsections 609 and 610, and decoding sections 612 and 613.

[0155] The following description will explain a manner how a mobilestation acquires synchronization with a base station when it is turnedon with reference to the case illustrated in FIG. 2 where a time slot totransmit a forward link common control channel signal including asynchronization control channel signal is provided once every four timeslots with three other time slots inserted.

[0156] When mobile station 600 is turned on, it does not know anassignment and timing of time slots for reverse link and forward linkbecause it does not acquire synchronization with a base station yet.

[0157] Then mobile station 600, as illustrated in FIG. 8, integrates acorrelation value of a received signal with a spreading code of forwardlink synchronization control channel at each sample timing within a fourtime slots length 701 starting from an arbitrary time t1 and repeats theintegration at four time slots intervals.

[0158] When the number of integration times is increased, since noisecomponent is reduced, it is detected that an integration value ofcorrelation value at sampling timing 702 illustrated in FIG. 8 thatconforms to a timing of the synchronization control channel signalbecomes larger than that at other sampling timing.

[0159] However, as the number of integration times is too increased, asampling timing by mobile station 600 shifts from the target timingbecause mobile station 600 does not acquire synchronization with thebase station yet. Therefore too large number of integration times makesit difficult to detect timing 702 for synchronization control channelsignal.

[0160] When common control channel signals including synchronizationcontrol channel signals are not provided at certain intervals, it isdifficult to reduce the noise component by the integration describedabove, making it difficult to detect a timing of synchronization controlchannel signal.

[0161] However, when common control channel signals includingsynchronization control channel signals are provided at certainintervals even though the numbers of time slots assigned for reverselink and forward link are varied, it is possible to execute integrationat the certain intervals, thus facilitating a detection of the timing ofsynchronization control channel signal.

[0162] In a configuration of mobile station 600 illustrated in FIG. 7,such synchronization acquisition by integration is executed in controlsection 617, however a synchronization section (not shown) may beprovided besides control section 617.

[0163] As described above, according to the fifth embodiment, a mobilestation detects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

[0164] (Sixth Embodiment)

[0165]FIG. 9 is a frame diagram illustrating an assignment of time slotsat a communication frame applied in a CDMA/TDD mobile communicationsystem according to the sixth embodiment of the present invention.

[0166]FIG. 9 illustrates an example where one frame 801 is divided intosixteen time slots 0 to 15. In FIG. 9, 802 indicates a time slot alwhich a forward link common control channel signal is provided, 803indicates a time slot at which a forward link user information channelsignal is provided, and 804 indicates a time slot at which a reverselink user information channel signal is provided.

[0167] In other words, one frame 801 is divided into sixteen time slotsso as to provide forward link common control channel signals includingsynchronization control signals at the eight time slots 0, 2, 4, 6, 8,10, 12 and 14, forward link user information channel signals at the timeslots 1, 5, 9 and 13, and reverse link user information channel signalsat the time slots 3 and 11.

[0168] The transmission power control operation of control section 617in mobile station 600 illustrated in FIG. 7 is explained with referenceto FIG. 9.

[0169] Since the forward link user information channel is an dedicatedchannel between a mobile station 600 and a base station, thetransmission power is controlled so that reception quality at mobilestation 600 meets a predetermined requirement.

[0170] On the other hand, since forward link common control channel is acommon channel, the transmission power control is not performed based ona requirement of reception quality at mobile station 600. As a result,the reception quality sometimes deteriorates temporarily due to fading.

[0171] In the case of performing a transmission power control forreverse link under open-loop control, the similarity of propagationpaths of reverse link and forward link is used. In this case, when atime interval between a forward link time slot to measure a receptionquality and a revere link time slot to transmit, the similarity ofpropagation path conditions of reverse link and forward link becomeslow, resulting in a reduction of accuracy of the transmission powercontrol.

[0172] The high reception quality introduces a more accurate estimationof propagation path conditions, however the propagation path conditionchanges as an interval between reception and transmission is increased.

[0173] Taking the above problems into consideration, a propagation pathcondition is estimated by combining a reception quality at each timeslot with an appropriate weight. In the case where the propagation pathcondition changes rapidly, a weight for a common control channel signalat the time slot 2 just before the time slot 3 to be transmitted is sethigh and weights for a common control channel signal or user informationchannel signal at the other time slots are set low. It may be performedthat the weight for the common control channel signal at the time slot 2is set at 1 and the weights for a common control channel signal or userinformation channel signal at the other time slots are set at 0.

[0174] On the other hand, in the case where the propagation pathcondition changes slowly, since it is possible to estimate thepropagation path condition with a high accuracy, a weight for a userinformation channel signal at the time slot 1 is set high and weightsfor common control channel signals at the time slots 0 and 2 are setlow. It may be performed that the weight for the user informationchannel signal at the time slot 1 is set at 1 and weights for commoncontrol channel signals at time slots 0 and 2 are set at 0.

[0175] In addition, the above case describes about the transmissionpower control of the reverse link user information channel signal at thetime slot 3, however the same processing is performed to thetransmission power control of the reverse link user information channelsignal at the time slot 11.

[0176] The above case further describes about the example where threetime slots just before the time slot to be transmitted are used tocombine with weights, however it is also preferable to use forward linkchannel signals at time slots before the three time slots.

[0177] In this case, the above example corresponds to the case whereweights for channel signals at time slots four time slots before thetime slot to be transmitted are set at 0. In addition, the above casedescribes that forward user information channel signals are provided atforward link time slots except for forward link time slots at whichcommon control channel signals are provided, however the same processingis performed in another case where forward link user information channelsignals and forward link common control channel signals are provided atthe same time slots.

[0178] Further, user information channel signals may be provided only atforward link time slots without being provided at reverse link timeslots. This case corresponds to weights for user information channelsignals being set at 0.

[0179] In addition, a propagation path condition is estimated bycombining signals with weights in the above case, however it is alsopreferable to predict a propagation path condition via which a time slotwill be transmitted using a time transition of the estimated propagationpath condition to control transmission power.

[0180] Further, in the above case, the transmission power control isperformed only under the open-loop control. However, the same processingis performed in the transmission power control under the combination ofclosed-loop control where a base station instructs transmission power toa mobile station via a forward link.

[0181] As described above, according to the sixth embodiment, a mobilestation detects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

[0182] Further, the mobile station measures a reception quality of aforward link common control channel signal provided at a time slot justbefore a time slot of a reverse link user information channel signaleven though the reverse link user information channel signal is providedat any reverse link time slot, thereby enabling an effective open-loopcontrolled transmission power control even when a propagation pathcondition changes rapidly.

[0183] (Seventh Embodiment)

[0184]FIG. 10 is a frame diagram illustrating an assignment of timeslots at a communication frame applied in a CDMA/TDD mobilecommunication system according to the seventh embodiment of the presentinvention.

[0185]FIG. 10 illustrates an example where one frame 901 is divided intosixteen time slots 0 to 15. In FIG. 10, 902 indicates a time slot atwhich a forward link common control channel signal is provided, 903indicates a time slot at which a forward link user information channelsignal is provided, and 904 indicates a time slot at which a reverselink user information channel signal is provided.

[0186] In other words, one frame 901 is divided into sixteen time slotsso as to provide forward link common control channel signals includingsynchronization control signals at the eight time slots 0, 2, 4, 6, 8,10, 12 and 14, forward link user information channel signals at the timeslots 5 and 10, and reverse link user information channel signals at thetime slots 3 and 11.

[0187] The transmission power control operation of control section 617in mobile station 600 illustrated in FIG. 7 is explained with referenceto FIG. 10. In addition, the explanation will describe the case where aweight for forward link channel signal provided at a time slot justbefore a time slot to be transmitted is 1 and weights for the otherforward link channel signals are 0.

[0188] A common control channel signal is provided at the time slot 2just before the time slot 3 to be transmitted. Accordingly, thetransmission power control is performed based on a reception quality ofthe forward link common control channel signal at the time slot 2.

[0189] On the other hand, both common control channel signal and userinformation channel signal are provided at the time slot 10 just beforethe time slot 11 to be transmitted. Accordingly, it is possible toperform the transmission power control based on both reception qualitiesof the forward link common control channel signal and user formationchannel signal.

[0190] Two correction detection sections are necessary to measure bothreception qualities of the forward link common control channel signaland user information channel signal. However, a single correlationdetection section is enough by providing a configuration where bothreception qualities can be switched to measure.

[0191] In a configuration where a reception quality of the forward linkcommon control channel signal is measured, the transmission powercontrol is performed based on the reception quality of the forward linkcommon control channel signal that has a lower accuracy, not dependingon the time slot assignment of user information channel signal forforward and reverse links, even when a forward link user informationchannel signal is provided at a slot just before a slot at which areverse link user information channel signal is provided.

[0192] Therefore, an effect of transmission power control is decreased.However, by providing a configuration where a channel to measure areception quality is switched to a user information channel when aforward link user information channel signal is provided at a slot justbefore a slot at which a reverse link user information channel signal isprovided, it is possible to measure the reception quality of the userinformation channel signal measurable with a high accuracy, therebyenabling an effective transmission power control of the reverse linkuser information channel signal.

[0193] As described above, according to the seventh embodiment, a mobilestation detects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

[0194] Further, the mobile station switches a reception quality of aforward link common control channel signal and that of a forward linkuser information signal provided at a time slot just before a time slotof a reverse link user information channel signal even though thereverse link user information channel signal is provided at any reverselink time slot, thereby enabling an effective open-loop controlledtransmission power control even when a propagation path conditionchanges rapidly.

[0195] As been obvious from the above-mentioned explanation, accordingto the present invention, it is possible for a mobile station to reducea acquisition time of synchronization with a base station even when anassignment of time slots for forward and reverse links is changedcorresponding to an information volume in the case where the informationvolumes of forward and reverse links are asymmetry, thereby enabling theopen-loop controlled transmission power control to function effectively.

[0196] This application is based on the Japanese Patent Application No.HEI10-78317 filed on Mar. 10, 1998, entire content of which is expresslyincorporated by reference herein.

In the claims:
 1. A base station apparatus in a CDMA/TDD communicationsystem that employs a communication frame divided into a plurality oftime slots, each of which is assigned one of a forward link and areverse link of the communication system, the base station apparatuscomprising: an assignor that assigns a forward link common controlchannel to position fixed time slots disposed at regular intervals amongthe plurality of time slots; and a controller that assigns a forwardlink user information channel, to time slots other than time slotsimmediately following the position fixed time slots, and that assigns areverse link user information channel to time slots other than theposition fixed time slots and the time slots assigned to the forwardlink user information channel.
 2. The base station apparatus of claim 1,the forward link common control channel comprising a synchronizationcontrol channel.
 3. The base station apparatus of claim 1, wherein saidassignor assigns the common control channel to position fixed time slotsthat are disposed at every other time slot.
 4. A CDMA/TDD communicationmethod that employs a communication frame divided into a plurality oftime slots, each of which is assigned to one of a forward link and areverse link, the method comprising: assigning a forward link commoncontrol channel to position fixed time slots disposed at regularintervals among the plurality of time slots; assigning a forward linkuser information channel to time slots other than time slots immediatelyfollowing the position fixed time slots; and assigning a reverse linkuser information channel to time slots other than the position fixedtime slots and the time slots assigned to the forward link userinformation channel.
 5. A base station apparatus in a communicationsystem that employs a communication frame divided into a plurality oftime slots, each of which is assigned one of a forward link and areverse link of the communication system, the base station apparatuscomprising: an assignor that assigns a forward link common controlchannel to position fixed time slots regularly spaced everypredetermined number of time slots; and a controller that assigns aforward link user information channel, to time slots other than timeslots immediately following the position fixed time slots, and thatassigns a reverse link user information channel to time slots other thanthe position fixed time slots and the time slots assigned to the forwardlink user information channel.
 6. The base station apparatus of claim 5,the forward link common control channel comprising a synchronizationcontrol channel.
 7. The base station apparatus of claim 5, wherein thepredetermined number of time slots comprises two time slots.
 8. The basestation apparatus of claim 5, wherein the predetermined number of timeslots comprises four time slots.